ELSA LANCOM Business 6000, Руководство пользователя

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Technical basics
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ELSA LANCOM Business 6000
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EN
The sequence of the entries is important here: They are processed from top
to bottom. The router sorts entries automatically: Firstly by network masks, in
descending order. Then by the IP addresses, in ascending order. This places
the 'HEAD OFFICE' entry at the very end of the list. If this entry were at the
top of the list, the
router would send all (!) data packets not belonging to the
local network to the network of the head office.
7.5.2 TCP/IP packet filters
You can use your entries in the routing table to determine quite precisely
which data should be transferred. Additionally, you can use the '0.0.0.0' entry
in the 'Router-name' field to reject whole groups of IP addresses.
Occasionally, you may wish to restrict a transmission even further. You can
do this using a characteristic of TCP/IP, which is to send port numbers for
destination and source as well as the source and destination IP addresses
with a data packet. The destination port in a data packet stands for the
service to be addressed in the TCP/IP network. The destination ports are fixed
for the various services on the TCP/IP network (see also 'TCP/IP-ports' in the
reference section). The source ports, on the other hand, may be selected
freely within certain ranges.
The router can check the source and destination ports of data packets using
the TCP or UDP protocols. It can then deduce the purpose of the data from
these ports. For example, FTP accesses or Telnet sessions can be identified.
192.168.130.0 255.255.255.0 192.168.140.123 0 All data packets with the destination IP
addresses 192.168.130.x are sent to the
locally available router with the IP address
192.168.140.123.
192.168.0.0 255.255.0.0 0.0.0.0 0 Excludes transmission of all data packets to
networks using private address spaces.
172.16.0.0 255.255.0.0 0.0.0.0 0
10.0.0.0 255.0.0.0 0.0.0.0 0
224.0.0.0 224.0.0.0 0.0.0.0 0
255.255.255.255 0.0.0.0 HEAD OFFICE 2 All data packets which cannot be allocated to
the entries listed above are transmitted to the
HEAD OFFICE remote station.
IP address Netmask Router Dist. This is what happens: